How to center title and change menu

Hi!

I use child-theme Vaaka, but I’m sure that i should search help here.
My site: https://www.ajkub.pl

I want change few things in Saga theme, but I haven’t idea how to do it. For sure, I need to change some css lines, but which?

My requests:
1) I want center site name and site description (it should works on every screen size).
2) I want change menu from drop-down to normal menu in one line.

Both changes should look similar to this theme: https://www.ads-software.com/themes/match/

Sorry for my language skill ??